Detection, quantification, isolation and purification of target biomaterials, such as viruses and biomacromolecules (including constituents or products of living cells, for example, proteins, carbohydrates, lipids, and nucleic acids) have long been objectives of investigators. Detection and quantification are important diagnostically, for example, as indicators of various physiological conditions such as diseases. Isolation and purification of biomacromolecules are important for therapeutic uses and in biomedical research. Biomacromolecules such as enzymes which are a special class of proteins capable of catalyzing chemical reactions are also useful industrially; enzymes have been isolated, purified, and then utilized for the production of sweeteners, antibiotics, and a variety of organic compounds such as ethanol, acetic acid, lysine, aspartic acid, and biologically useful products such as antibodies and steroids.
In their native state in vivo, structures and corresponding biological activities of these biomacromolecules are maintained generally within fairly narrow ranges of pH and ionic strength. Consequently, any separation and purification operation must take such factors into account in order for the resultant, processed biomacromolecule to have potency.
The use of certain ionic polymers, especially cationic polymers, for the flocculation of cell and/or cell debris, as well as for the precipitation of proteins, is known. Similarly, ionic polymers have been used to modify filtration media to enhance the removal of impurities from process streams in depth filtration or membrane absorber type applications. The effectiveness of these flocculants is typically reduced as the conductivity of the media being processed increases, i.e. as the salt content increases. There is a need in the art for polymeric materials with increased affinity for biological species under high ionic strength conditions.
Chromatographic separation and purification operations can be performed on biological product mixtures, based on the interchange of a solute between a moving phase, which can be a gas or liquid, and a stationary phase. Separation of various solutes of the solution mixture is accomplished because of varying binding interactions of each solute with the stationary phase; stronger binding interactions generally result in longer retention times when subjected to the dissociation or displacement effects of a mobile phase compared to solutes which interact less strongly and, in this fashion, separation and purification can be effected.
Most current capture or purification chromatography is done via conventional column techniques. These techniques have severe bottlenecking issues in downstream purification, as the throughput using this technology is low. Attempts to alleviate these issues include increasing the diameter of the chromatography column, but this in turn creates challenges due to difficulties of packing the columns effectively and reproducibly. Larger column diameters also increase the occurrence of problematic channeling. Also, in a conventional chromatographic column, the absorption operation is shut down when a breakthrough of the desired product above a specific level is detected. This causes the dynamic or effective capacity of the adsorption media to be significantly less than the overall or static capacity. This reduction in effectiveness has severe economic consequences, given the high cost of some chromatographic resins.
Polymeric resins are widely used for the separation and purification of various target compounds. For example, polymeric resins can be used to purify or separate a target compound based on the presence of an ionic group, based on the size of the target compound, based on a hydrophobic interaction, based on an affinity interaction, or based on the formation of a covalent bond. There is a need in the art for polymeric substrates having enhanced affinity for viruses and other biological species to allow selective removal from a biological sample. There is further need in the art for ligand functionalized membranes that overcome limitations in diffusion and binding, and that may be operated at high throughput and at lower pressure drops.